Modern high performance Coriolis gyroscope sensors typically contain vibrating structures, for example using microelectromechanical systems (“MEMS”), which are designed to operate with very high Q-factors, or magnification factors. This results in a sensor having a very low natural bandwidth.
The Q-factor of most MEMS sensors can be highly variable, for example due to manufacturing tolerances, and can also vary in use due to, for example, temperature variations. This may result in significant variations in the Q-factor, and the natural bandwidth of the sensor, in use. In addition the resonant frequency may also have independent tolerances and temperature variations, causing similar effects on the frequency response.
Most high performance systems require some sort of frequency response shaping. A number of techniques can be used to shape the frequency response of a MEMS sensor. For example, pole-zero cancellation can be used but this may result in inconsistent responses at low frequencies.
FIG. 1 shows the above-described effects using a conventional gyroscope. When considered over the full bandwidth of interest the frequency response appears to conform to a simple second order system, but if the low frequency range is looked at in more detail it can be seen to deviate quite significantly. Low frequency gain variations 10 can be seen, which may be acceptable for low performance systems. However, these may become problematic for high performance and/or highly dynamic systems.
It is desired to provide an improved method of sensing a rotation rate using a vibrating structure gyroscope.